Process of treating cellulose-acetate reaction mixtures



Nov. 10, 1925.

E. S. FARROW, JR

PROCESS OF TREATING CELLULOSE ACETATE REACTION MIXTURES Filed Aug. 4. 1924 A TT ORNEY.

" cori-raux, or ROCHESTER, NEW Yoan, A .coitronarioivor NEW YORK.

j 2Pitooiizss'or TBEAT'ING cELLULosa-*AVCETATE anncrioilrfirixrunrsr- 4 L 5 applicama .inea August 4, i924. 'serialA No. v'2150,11'9.A -v

.Baia 4known that I, EDWARD-'sq FAR'RW',

rl`his veiitionA relates'* to.' processes fof* treating cellulose acetate"reactionmixtures.4

Oneobject'of theinventin is to provide a' 'l process lforl'treatimg. celluloseacetate re- Aaction mixtures which areespecial'ly.viscous, s o as to simply and reliably 4precipitate and subdivide the cellulose acetate in c-ondition vfor further purification or A treatment. 1

Another Objectis to v'provide-a -process which l'may becarriedout in f ajgrelatively small working or `:tacto'ryspace. A still further object is to'piovide aprocess in which the `precipi'tating Vliquid can be kept small, relaltive to l,the reaction-mixture, so as to provide acon'ce-ntrated liquor from which byproducts and excess ingredients can be more readily recovered. Yet another object of the i s invention is toprovide. a process in which the precipitating liquid may, if desired, be added-anddrawn oit' continuously Other "objects -Will hereinafter appear.

" In the accompanying drawing thesingle ligure" is a diagrammatic side. elevation,

partly in vertical section, showing one form ofv apparatus in which myproce'ss may be conveniently carried out, the relative sizes oli the parts being exaggerated for the .sake fof clearness. v I.

' Cellulose acetate reaction mixtures con- 40 tain in solution, or partial solution, cellulose acetate and various by-products or excess ingredients. It is highly desirable lto separate the cellulose acetateqfrom the other ingredients, and 'moreover obtain it in a subdivided form. It is alsodesirable tol recover theby-products and excessin gredient's. But such separation and recovery present a dirliicult technical problemy when the reaction mixtures are highly viscousa Mixtures of unusually` great viscosity are obtained, for example, when rela- I tively small amounts. of acetic acid are present as a solvent; and they are likewise obtained when the maximum amount of vcellulose acetate is-dissolved in nitric acid @stirred up in it.

closure in vmy (3o-'pending application, No.

670,173-, tiled Oct. 22,11923,1f or process of *treating cellulose acetate.,

-Reaction mixtures of heavy viscosity can iiot'be 4poured into Water .to precipitate the 'cellulose acetate in the customary manner.

l f EDWARb s; aannemen., or 4Rocli'eliiisrnn, NEvr'YoRiz, AssrGNoa TOEASTMAN KODAK l 1 for ihydrolysis,1in accordance v." tlledisl Nor can they be efficiently dumped en masse into a large body ,of Water and then be I have found that the problem -can be solved by associating Water with the mass only gradually, and forcing it mechanically through the mass by suitable agitating means, such as blades. Andl I prefer to keep the amount of Water, which is-in con'- tact with the mass, less than the volume of the latter. For 'exam-ple', I may dump a reaction mass, which is too viscous to be poured Y and handled by the ordinary methods, into a lmixer of the type shown in U. S. Patent No. 534,96@ Pfleiderer, Feb.

261895, machine for mixing, kneading or otherwise treating plastick masses; The blades arethen set in motionJ and Wateris gradually added, say'by being poured, a relatively small amount at aetime, on the topot the mass as the blades are cutting through it. By keeping the total Water in the mixer at any one timerelatively small,

say less than the volume of the mixture, the--y apparatus in which the process is `carried out can be kept within small factory space, and the Water takes up the by-products and excess ingredients in strong solution. The liquoris drawn .oli when it becomes sufficiently concentrated for efficient recovery of the dissolved, materials. The liquor may be drawn 4ofi' and fresh Wateradded inter.-v mittently, or these Operations may be carried on continuously, which is convenient in large scale Work.

In this way the cellulose acetate gradually` becomes precipitated in a desirable state of?" subdivision. The Water is carried uniform-y ly through the mass in small amounts-by each blade movement, so that veveiitually'all ofthe particles of the mass are treated. This tends toward uniformity in the action as distinguished from the results obtained ies when a large mass or lump of the dilicultly manipulable mixture is dumped into a large body of'water, which acts' on it only at thc outer surface, and dilutes the extracted ma:-

terials so that their recovery is made diffv iicult. When the action has been carried on to the point where the precipitation, subdivision, and extraction are suiiiciently complete, the materials are removed from the mixer and final washing, if necessary,

and any other usual or desired treatments then take place in the usual way.

Referring to the drawing, 1 is the main vessel in which the process may be carried out. rI`his is preferably air-tight except for the piping'hereinat'ter described. Its bottom is divided into two troughs 2, 3 above which are located mixing blades 4 rotated with shafts 5 by anyk'suitable means (not shown). I prefer to'have the blades of the well known form in which they not only cut the material transversely but impart a llongitudinal movement to it also.

Entering into the top of vessel l and dis- ,charging at a point closely adjacent -tlie meeting point of the paths of the blades 4 is a pipe 6 controlled by a valve 7. The highly viscous reaction mixture 8 is loaded into the vessel, say through the fixture 9 l5 until its -upper face is approximately at the maximum height attained by the blades 4,

although it may be dropped somewhat be! low this. lI`he lower end ot pipe 6 may be above the upper surface otl the mixture 8,

or may be beneath it, say a slight distance asshown in the drawing. In the top of the vessel 1 there is a removable cover 10 through which the product may be conveniently unloaded. In the side of the vessel 3f l there are one or more pipes 11, 12 controlled by valve `13, 14, through which the water, carrying soluble materials, suchr 'as acetic acid, may be removed. The inner ends of the pipes are preferably screened at 15.I `40 Ordinarily it is sufficient to use merelythe upper pipe 11 which is adjacent the normal Y working level of the water 16 in the vessel.

In brief the viscous reaction mixture 8 is loaded into the vessel l through fixture 9 until its upper surface assumes the proper 'level' Vater is then added through pipe 6 and the blades cut into the mixturefS so that water is gradually brought through the entire viscous mass by the blades andthe cellulose acetate is precipitated in subdivided form. Fresh water is constantly being cut into the mass, andv water containing acetic acid and other soluble materials' from the mass is constantly being evolved from the .55 upper surface of the mass. This solution of acetic acid is then drawn .0H through the pipes 11 or 12. 4'Ihe flow of water from pipe 6 and its exit through pipe 11 may be cor-` related so that the operation is continuous. Having thus" described my invention, what I claim as new and desire to secure by Letters Patent is: y

1. The process of separating and subdividing celluloseacetate from a reaction mix ture of high viscosity, which comprises forcing blades through said mixture and gradually adding liquid water during said forcing of said bladesuntil cellulose acetate is precipitated in subdivided form.

2. 'Ihe process of separating and subdivi-ding cellulose acetate from a reaction mixture of high viscosity, which comprises fore ing blades through said mixture and maintaining liquid water in contact with said mixture, during said forcing ot' said blades, the volume of water in .contact with said mixl ture being less than the volume of the latter,

ture of high viscosity, which comprises forcing blades through said mixture, supplying water for said blades to carry through the mixture, and drawing otf water through the mixture and containing Water-soluble materials from said mixture, the volume of water in contact with said mixture at all times being kept less than the volume ot" said mixture.

5. The process of separating-and subdividing cellulose acetate from a reaction mixture of high viscosity, which comprises forcing blades through said mixture, supplying water for said blades to carry through the mixture, and drawing off water ca'rried through the mixture and containing watersoluble materials from said mixture, and recovering said materials from the water.

Signed at Rochester, New York this 24th .day of July, 1924.'

EDWARD s. FARRow, Ja. 

